Installing this mod causes several bugs with the Tough As Nails canteen, which are immediately fixed if this mod is uninstalled, i.e. it 100% is this mod causing the issues.

• Drinking from a water canteen refills more thirst than it should / more than it displays it should.
• The third time a filled Canteen is used, it replenishes less than the other two times.
• A Canteen with purified water still has the same chance to apply the thirst debuff as one filled with unpurified water.
• The Purified Water Canteen displays that it replenishes 1.5 drops of thirst, while it should replenish 3 drops of thirst, (but of course because of the aforementioned bugs it actually replenishes even more than that).

This mod also causes quite a weird issue with the Millenaire mod, which may hint at what the issue is. Similar to the Canteen, Millenaire adds food items which have a durability and can be consumed multiple times. None of these have any thirst replenishing values by default, but by editing the Tough As Nails config, you can give them specific thirst values.
In this case the bug is that, while this mod is installed, food items with durability from Millenaire which have been given a thirst value in the config do not replenish that amount of thirst, while when this mod is not installed, they replenish the amount of thirst they are configured to replenish with no issues.

No idea what could be causing all this, but it is definitely this mod causing it, because removing it from my mods folder solves all the issues.